Stemflow Research Articles

Effects of aphid infestation on the biogeochemistry of the water routed through European beech (Fagus sylvatica L.) saplings

Mass outbreaks of herbivore insects perturb the functional properties of forests, by substantially altering water and nutrient cycling of infested trees. Less clear is how low to moderate herbivory affects the vertical flow of nutrients from trees to the soil. We report on the effects of low to moderate infestation levels of the woolly beech aphid (Phyllaphis fagi L.) on the nutrient dynamics and hydrology of European beech (Fagus sylvatica L.). We traced the vertical dynamics of macro and micronutrients via throughfall (TF), stemflow (SF) and Oa litter leachates from potted saplings underneath infested and uninfested control trees. The low infestation levels were insufficient to significantly alter TF and litter leachate composition, although, on average, the release of K and DOC and the immobilization of N (NH4–N) in TF solution were more pronounced under aphid infestation. SF chemistry was significantly altered by aphid activity exhibiting intensified fluxes of K (+159 %), Mg (+82 %), Mn (+93 %), S (+86 %), SO4–S (+62 %), DOS (+137 %), DOC (+51 %) and DON (+62 %), compared to control trees. SF is likely enriched by low and mid-level aphid activity due to its increased residence time in the canopy. It has interaction with large areas of aboveground vegetative surface area representing a cumulative flux of solutes and particulates from both foliar and woody surfaces from above-lying portions of the canopy. Accordingly, SF might be a useful indicator to evaluate the impact of sap- and leaf-feeding herbivores on forest ecosystems.

The importance of considering rainfall partitioning in afforestation initiatives in semiarid climates: A comparison of common planted tree species in Tehran, Iran

As plantations become increasingly important sources of wood and fiber in arid/semiarid places, they have also become increasingly criticized for their hydrological impacts. An examination and comparison of gross rainfall (GR) partitioning across commonly-planted tree species (Pinus eldarica, Cupressus arizonica, Robinia pseudoacacia, and Fraxinus rotundifolia) in semiarid regions has great value for watershed and forest managers interested in managing canopy hydrological processes for societal benefit. Therefore, we performed a field study examining GR partitioning into throughfall (TF), stemflow (SF), and rainfall interception (I) for these species in the semiarid Chitgar Forest Park, Tehran, Iran. An advantage to our study is that we explore the effects of forest structural differences in plantation forests experiencing similar climatic factors and storm conditions. As such, variability in GR partitioning due to different meteorological conditions is minimized, allowing comparison of structural attributes across plantations. Our results show that commonly-selected afforestation species experiencing the same climate produced differing stand structures that differentially partition GR into TF, SF, and I. P. eldarica might be the best of the four species to plant if the primary goal of afforestation is to limit erosion and stormwater runoff as it intercepted more rainfall than other species. However, the high SF generation from F. rotundifolia, and low GR necessary to initiate SF, could maximize retention of water in the soils since SF has been shown to infiltrate along root pathways and access groundwater. A consideration of GR partitioning should be considered when selecting a species for afforestation/reforestation in water-limited ecosystems.

Rainfall partitioning characteristics of three typical sand-fixing shrubs in Horqin Sand Land, north-eastern China

Rainfall partitioning by vegetation affects water balance and utilization by plants. Caragana microphylla, Hedysarum fruticosum, and Salix gordejevii are three typical, morphologically different sand-fixing shrubs in Horqin Sand Land. However, few studies have compared rainfall partitioning by these shrubs. We examined rainfall partitioning differences among these shrubs in Horqin Sand Land, north-eastern China. On average, throughfall, stemflow (SF), and interception for C. microphylla accounted for 64.2, 11.0, and 24.8% of the individual incident rainfall, respectively; for H. fruticosum, they accounted for 71.2, 6.3, and 22.5%; and for S. gordejevii, they accounted for 75.3, 5.3, and 19.4%. The average funneling ratio for H. fruticosum (162.7 ± 33.2) was larger than that for C. microphylla (100.1 ± 16.9) and S. gordejevii (106.2 ± 23.1). Rainfall partitioning was significantly correlated with canopy area, branch number, and stem basal area for C. microphylla and S. gordejevii. SF volumes of 3,167, 676, and 2,210 L were estimated to have channeled into the plots for C. microphylla, H. fruticosum and S. gordejevii, respectively, indicating that C. microphylla is more effective in channeling SF to the root zone. These results suggest that C. microphylla may be more advantageous for sand-fixing and vegetation restoration in sand lands.

Characters related to higher starch accumulation in cassava storage roots.

Cassava (Manihot esculenta) is valued mainly for high content starch in its roots. Our understanding of mechanisms promoting high starch accumulation in the roots is, however, still very limited. Two field-grown cassava cultivars, Huanan 124(H124) with low root starch and Fuxuan 01(F01) with high root starch, were characterised comparatively at four main growth stages. Changes in key sugars in the leaves, stems and roots seemed not to be strongly associated with the final amount of starch accumulated in the roots. However, when compared with H124, F01 exhibited a more compact arrangement of xylem vascular bundles in the leaf axils, much less callose around the phloem sieve plates in the stems, higher starch synthesis-related enzymatic activity but lower amylase activity in the roots, more significantly up-regulated expression of related genes, and a much higher stem flow rate (SFR). In conclusion, higher starch accumulation in the roots results from the concurrent effects of powerful stem transport capacity highlighted by higher SFR, high starch synthesis but low starch degradation in the roots, and high expression of sugar transporter genes in the stems. A model of high starch accumulation in cassava roots was therefore proposed and discussed.

The Stem Heat Balance Method to Measure Transpiration: Evaluation of a New Sensor

The measurement of crop transpiration (Tcrop) under field conditions and throughout the growing season is difficult to obtain. An available method uses stem flow gauge sensors, based on the conservation of energy and mass, where the calculated sap flow (F) is a direct measure of Tcrop. This method has been extensively tested on agronomic, horticultural, ornamental aspects and tree crops and the general consensus is that F is a measure of Tcrop. A new sap flow gauge (EXO-SkinTM Sap Flow) sensor, with different placement and number of thermocouples, compared to the original sensor, was introduced, resulting in a different energy balance equation to calculate F. Our objective was to compare values of Tcrop obtained with the new sensor on cotton (Gossypium hirsutum, L) plants to values measured with lysimeters. For this purpose, cotton plants were grown in 11-liter pots in a greenhouse experiment and hourly and daily values of Tcrop were compared for eight days. We used linear regression analysis to compare the hourly and daily values of Tcrop measured with the sensor to corresponding values measured with lysimeters on the same plant. Using a t-test (p > 0.05) we tested if the slope of the line was significantly different than 1 and if the intercept was significantly different than 0. This test indicated that there were no statistical differences between hourly and daily values of Tcrop measured with the new sensor and with the lysimeters. The main advantage of the new sensor is the flexibility of the new heater, allowing for better thermal contact between the plant stem and the temperature sensors. Further, the new sensor requires less wiring and copper connectors, and the number of channels used in a datalogger to record the output from the sensor is reduced by 25%. We conclude that the new sensor correctly measures Tcrop and that additional experiments with field grown plants are required to test the sensor at higher values of Tcrop.

Influence of Canopy Architecture on Stemflow in Agroforestry Trees in Western Himalayas

Rainfall event on a tree can be partitioned into throughfall, interception loss and stemflow. In this study, stemflow was measured for 39 rainfall events in 5-year-old plantations of 3 trees each, belonging to Morus alba and Grewia optiva in Dehradun, India. Diameter of selected Morus and Grewia trees varies from 7 to 9.3 and 8.12 to 10 cm respectively, whereas height varies from 4 to 4.5 and 5.5 to 6.5 m respectively. The minimum and maximum rainfall events recorded during the study period were 1.01 and 121.70 mm per day respectively. When the rainfall magnitude was less than or equal to 50 mm and more than 50 mm, stemflow volume from Morus was approximately 2.72 and 1.85 fold higher respectively, compared to Grewia . Maximum stemflow volume recorded for Morus and Grewia was 48,065 and 30,633 ml with respect to rainfall magnitude of 109.58 and 121.70 mm respectively. The generation of higher stemflow volume in case of Morus is due to concave orientation of branches and leaves. Results showed that a significant amount of nutrients leached from Grewia and Morus through stemflow process.

Stem flow of seed-maize under alternate furrow irrigation and double-row ridge planting in an arid region of Northwest China

Maize is widely planted throughout the world and has the highest yield of all the cereal crops. The arid region of Northwest China has become the largest base for seed-maize production, but water shortage is the bottleneck for its long-term sustainability. Investigating the transpiration of seed-maize plants will offer valuable information for suitable planting and irrigation strategies in this arid area. In this study, stem flow was measured using a heat balance method under alternate furrow irrigation and double-row ridge planting. Meteorological factors, soil water content (θ), soil temperature (Ts) and leaf area (LA) were also monitored during 2012 and 2013. The diurnal stem flow and seasonal dynamics of maize plants in the zones of south side female parent (SFP), north side female parent (NFP) and male parent (MP) were investigated. The order of stem flow rate was: SFP>MP>NFP. The relationships between stem flow and influential factors during three growth stages at different time scales were analyzed. On an hourly scale, solar radiation (Rs) was the main driving factor of stem flow. The influence of air temperature (Ta) during the maturity stage was significantly higher than in other periods. On a daily scale, Rs was the main driving factor of stem flow during the heading stage. During the filling growth stage, the main driving factor of NFP and MP stem flow was RH and Ts, respectively. However, during the maturity stage, the environmental factors had no significant influence on seed-maize stem flow. For different seed-maize plants, the main influential factors were different in each of the three growing seasons. Therefore, we identified them to accurately model the FP and MP stem flow and applied precision irrigation under alternate partial root-zone furrow irrigation to analyze major factors affecting stem flow in different scales.

ESCOAMENTO DA ÁGUA DA CHUVA PELO TRONCO DAS ÁRVORES EM UMA FLORESTA ESTACIONAL SEMIDECIDUAL

RESUMOEste trabalho foi desenvolvido na Estação de Pesquisas, Treinamento e Educação Ambiental Mata do Paraíso, situada no Município de Viçosa, na Zona da Mata de Minas Gerais, Brasil, e teve como objetivo avaliar o escoamento pelo tronco em um fragmento de Mata Atlântica, no período de agosto de 2009 a março de 2011. Para quantificar esse escoamento, foram demarcadas seis parcelas de 10 x 10 m, sendo em cada parcela adaptados coletores à base de poliuretano nos troncos das árvores com circunferência 15,0 cm. Um pluviômetro foi instalado em local aberto para quantificar a água diretamente da chuva. Além disso, realizou-se uma análise qualitativa dos indivíduos do escoamento pelo troco, avaliando a qualidade do fuste e da copa, posição no estrato da floresta e infestação de cipó. Em todo o período de análises, foram realizadas 75 medições. Nas parcelas de escoamento pelo tronco foram amostrados 126 indivíduos, distribuídos em 29 famílias e 59 espécies. A precipitação em aberto foi de 2.391,63 mm, e o escoamento pelo tronco somou 31,59 mm, ou 1,32% da precipitação em aberto. A espécie com maior escoamento pelo tronco foi a Euterpe edulis, com um volume médio de água escoado de 637,00 L. Das espécies com maior escoamento pelo tronco, 73,91% encontravam-se no estrato inferior da floresta, evidenciando que algumas espécies possuem algum tipo de adaptação morfológica para captação da água da chuva.

Effect of strip thinning on rainfall interception in a Japanese cypress plantation

Summary We examined the effect of strip thinning on rainfall interception (Ei) in a 32-year-old Japanese cypress plantation in central Japan. Strip thinning was conducted in the catchment in October 2011; that removed 50% of the stems. The gross precipitation (Pg), throughfall (TF) and stemflow (SF) were monitored in a 12-m × 13-m plot before and after thinning. Ei was calculated as the difference between Pg and the sum of TF and SF. The interception processes were illustrated using the revised Gash model with quantifying interception parameters. The results showed that the Gash model successfully predicted Ei on a rainy-season basis in both pre- and post-thinning periods. Thinning altered the interception components whereas the largest part during and after rainfall accounted for similar proportion in both periods. Additionally, after thinning, the annual TF rate was increased from 61.4% to 73.0%, whereas the annual SF rate was decreased from 9.8% to 6.1%, and the annual Ei rate was decreased from 28.7% to 20.8%. The summarized findings of previous studies indicate that the degree of decline in the Ei caused by thinning is related to Pg and the thinning ratio. These results provide useful information for understanding the changes in interception processes induced by thinning, and for acquiring a more accurate forecast of the effects of forest management practices on water resources in the watershed. The response in rainfall partitioning to strip thinning can also help us to acquire an integrated understanding of the changes in canopy water balance under different forest practices.

ChemiCl2+l Characteristics of Rain Water Collected from Subalpine Region of Mt. Gumwon

This study was carried out to analyze chemical characteristics with the water collected from stem flow, throughfall, and rainfall in the subalpine region of Mt. Geumwon and urban industrial forest area located in Saha-Gu, Busan, Korea as a control. According to season and region, the pH in the subalpine region of Mt. Geumwon was higher in the spring. The electrical conductivity (E. C.) in the subalpine region of Mt. Geumwon was 1.06∼1.1 times higher in the autumn than the control forest area. In the control forest area, the E.C. was 1.8 ∼2.8 times higher than in the subalpine region of Mt. Geumwon in the rainfall. Among cations analyzed using the rainfall collected in the subalpine region of Mt. Geumwon, Ca2

Nitrate isotopic composition reveals nitrogen deposition and transformation dynamics along the canopy-soil continuum of a suburban forest in Japan.

Heavy nitrogen (N) deposition often causes high nitrate (NO3(-)) accumulation in soils in temperate forested ecosystems. To clarify the sources and production pathways of this NO3(-), we investigated NO3(-) isotope signatures in deposition processes along the canopy-soil continuum of a suburban forest in Japan. The stable isotopes of N and oxygen (O) were used to trace the source and transformation dynamics of nitrate (NO3(-)) in two forest stands: a plantation of Cryptomeria japonica (coniferous tree; CJ) and a natural secondary forest of Quercus acutissima (broadleaf, deciduous tree; QA). The NO3(-) and ammonium (NH4(+)) concentrations were measured, as well as the δ(15)N and δ(18)O values of NO3(-), in rainfall, throughfall, stem flow, litter layer water, and soil water (10, 30, and 70 cm depths). Seasonal variations were observed in the δ(15)N values of throughfall and stem flow NO3(-) at both sites, and in the δ(18)O values of throughfall and stem flow NO3(-) at the QA site. The range in the δ(18)O values of rainfall and throughfall NO3(-) was large (65-70‰) but decreased dramatically to 2-5‰ in soil water at both sites. At the QA site, the δ(18)O values of stem flow NO3(-) decreased to 40‰ during several rain events, especially in the growing season. NO3(-) from atmospheric deposition was replaced by microbially generated NO3(-) mainly in the organic horizon and surface portion of the mineral soil under excess N deposition in this suburban forest. Microbial activity, including both immobilization and nitrification in organic-rich horizons near the surface, contributed to incorporating atmospheric NO3(-) quickly into the internal microbial N cycle. We also found evidence of microbial nitrification in the canopy of the QA stand during the growing season.

Evaluation of Sap Flow Sensors to Measure the Transpiration Rate of Plants during Canopy Wetting and Drying

Accurate measurement of transpiration is required to estimate the various components of evaporation losses during sprinkler irrigation. Among the methods, sap flow measurements have widely used for direct measurements of transpiration rate in plant. To evaluate the applicability of this method to field experiments involving canopy wetting (by sprinkler irrigation), stem flow measurements were compared with transpiration values estimated from successive mass measurements of small potted plants using pre-calibrated mini-lysimeters in a glasshouse at the University of Southern Queensland, during the period August–October 2010. From this study it was found that when the canopy was dry, the sap flow measurements mirrored the transpiration rate of plants with reasonable accuracy, overestimating the transpiration rate by about 11%. The measurements showed no evidence of time lag between sap flow and transpiration. Following wetting of the plant canopy the sap flow declined rapidly reflecting a decline in the transpiration rate transpiration and sap flow. Location of the sap flow gage on the stem was seen to be a factor with gages at different heights giving different sap flow rates again due to the buffering capacity of the stem.

Simulation of Gash Model to Rainfall Interception of Pinus tabulaeformis

Aim of study: In order to test the adaptability of revised Gash analytical model to canopy interception of Pinus tabulaeformis plantation, determine local parameters in the model, and analyze the sensitivity of the parameters to the simulated interception.Area of study: The throughfall experiment has been completed in Hebei province of China during 2010.Material and methods: During the experiment process, rainfall，throughfall and stemflow were measured and canopy interception was simulated with the revised Gash analytical model.Main results: The results show that the rate of measured throughfall, stem flow and canopy interception occupied to rainfall were 67.08%, 3.10% and 29.82%. Canopy storage capacity, stem storage capacity and Stemflow partitioning coefficient was 2.68 mm, 1.22mm and 0.03. Evaporation rate varied from 0.01 to 0.37 mm•h-1 and the ratio of evaporation and rainfall (E/R) ranged from 0.01 to 0.19 in rainfall periods.Research highlights: The revised gash model was able to accurately simulate the weekly canopy interception of Pinus tabulaeformis forest.Key words: Gash analytical model; Throughfall; Canopy interception; Pinus tabulaeformis plantation.

Comparison of interception, forest floor evaporation and transpiration in Pinus radiata and Eucalyptus globulus plantations

AbstractStudies of evapotranspiration (ET) processes in forests often only measure one component of total ET, most commonly interception. This study examined all three components of annual ET (interception, evaporation from the forest floor and transpiration) and the correlations between them at 18 plantation forest sites in two species. All plantations had closed canopies, and sparse or no understorey. Single‐sided leaf area index averaged 3.5 (standard deviation ±0.5) in Eucalyptus globulus Labill. and 6.1 (±0.8) in Pinus radiata D.Don.Measurements included annual totals of rainfall in the open and under the canopy, stem flow (four sites only), evaporation from the forest floor and transpiration by the overstorey. Interception (I) averaged 19% (±4.9) of annual rainfall in E. globulus compared with 31% (±11.1) in P. radiata. However, higher annual interception in P. radiata did not result in higher total ET because annual evaporation from the forest floor (E) averaged 29% (±4.9) of rainfall in E. globulus but only 15% (±3.5) in P. radiata. Hence, the relative contribution of annual I plus E to ET did not differ significantly between the two species, averaging 48% (±7.3) of annual rainfall in E. globulus compared with 46% (±11.8) in P. radiata. As reported previously, transpiration did not differ significantly between the two species either, but was strongly related to depth‐to‐groundwater. In closed canopy plantations, mean annual ET did not differ between the two species.We conclude that when grown in plantations under similar soil and climatic conditions, conifer and broad‐leaved tree species can have similar annual ET, once the canopy of the plantation has closed. Lower average annual interception in broad‐leaved trees was offset by higher soil evaporation. These results highlight the importance of measuring all components of ET in studies of vegetation water use. Copyright © 2014 John Wiley & Sons, Ltd.

Incident rainfall partitioning and canopy interception modeling for an abandoned Japanese cypress stand

Interception loss (Ei) in forests has been studied widely. However, Ei parameters and modeling as well as spatial patterns of throughfall (TF) in abandoned Japanese cypress (Chamaecyparis obtusa) plantations remain poorly documented. In this study, gross precipitation (PG), stemflow (SF), and TF were monitored in an unmanaged 32-year-old Japanese cypress stand throughout the 2011 rainy season. Results indicate that PG partitioning into TF, SF, and Ei were, respectively, 64.2 ± 3.6, 10.6 ± 0.6, and 25.2 ± 1.1 % of the 880.8 mm cumulative PG from 29 rainfall events. Direct throughfall proportion (p) and drainage from the canopy contributed about 14 ± 7 and 50 ± 21 % of the total TF for the events, respectively. The mean canopy storage capacity (S) was 2.4 ± 0.7 mm. The coefficient of variability (CV) of TF rate decreased asymptotically with increasing PG amount, ranging from 16 to 56 % with median 26 %. The CV of TF rate was not significantly correlated with canopy cover (r = 0.152, P = 0.521, n = 20) and distance from the nearest trunk (r = 0.196, P = 0.408, n = 20). Based on the revised Gash analytical model, the total simulated Ei was close to the observed, with a general underestimation magnitude of 5.7 %. The Ei components were quantified, and most of the interception loss (62.9 %) evaporated during rainfall, while 26.8 % evaporated after rainfall ceased. Climatic and forest structural parameters required by the model were identified and analyzed by sensitivity analysis, implying that the revised Gash analytical model is robust and reliable enough for abandoned Japanese cypress plantations in a maritime climate.

Online Appendix 1: Description of the major soil types within the central eastern communal conservancies, Namibia

The eastern communal conservancies are situated along the western fringe of the Kalahari basin. Under a very short rainfall gradient, the vegetation abruptly changes from microphyllous Acacia-dominated savannas to mesophyll savannas, dominated by Terminalia sericea and Combretum spp. We hypothesise that this is caused by changes in soil moisture availability brought about by changes in soil texture from loamy soils to deep sands (the ‘inverse texture effect’). For this analysis, we used vegetation and soils data derived from a recognisance survey of the natural resources of the study area. As the sites in the soil and vegetation surveys did not overlap, it was decided to use only synoptic data for the plant associations in the analysis. Non-metric multidimesional scaling ordination was utilised as ordination technique of the vegetation data and various environmental parameters, including soil texture, soil hydraulic parameters, climatic and fire regime parameters, were overlaid as biplots onto the resulting graph, as were various plant functional attributes particularly related to climatic conditions. The main environmental gradient identified within the study area is the rainfall gradient. This relatively short gradient, however, does not explain the marked change in vegetation observed within the study area. This change is attributed to the change in soil type, in particular, the soil texture and the associated soil hydraulic parameters of the soil. This gradient is closely correlated to leaf size, explaining the change from microphyll savannas to mesophyll savannas along the change from loamy to sandy soils. One of the lesser understood mechanisms for the survival of these mesophyll plants on sandy soils seems to be a deep root system, which is actively involved in water redistribution within the soil profile – by hydraulic lift, inverse hydraulic lift and stem flow. Conservation implications: Understanding these mechanisms will greatly assist in understanding savanna dynamics. With the threat of global climate change, we postulate that the vegetation will gradually change from the present mesophyll to a microphyll savanna, but that the grass sward will probably not develop very well. Shrub and tree removal (‘bush harvesting’) is likely to speed up the desertification process within this area.

Forest canopy interception loss exceeds wet canopy evaporation in Japanese cypress (Hinoki) and Japanese cedar (Sugi) plantations

The aim of this study is to evaluate rainfall partitioning at the forest canopy and reveal the physical process of canopy interception loss. Observations were conducted for 19 months in neighboring stands of Chamaecyparis obtusa Sieb. et Zucc. (Hinoki) and Cryptomeria japonica D. Don (Sugi). Cumulative amounts for the period showed that portions of throughfall (TF), stemflow (SF) and interception (IC) to rainfall (RF) for Hinoki were 65.3%, 9.1%, and 25.5%, respectively. Corresponding values for Sugi were 67.9%, 6.6%, and 25.5%. The smaller TF and larger SF in Hinoki than those in Sugi were induced by greater mean funneling ratio of a tree and greater tree density in Hinoki. Similar IC/RF would result from similar leaf area index. In analyses for rainfall events, rainfall period (RP) was defined as the period excluding short no-rainfall periods within an event, and rainfall intensity (RFI) was as RF/RP. In events with canopy saturation (RF ⩾ 10 mm), IC/RF was insensitive to RP and RFI. This was related to an increasing rate of IC with RFI. Evaporation for IC estimated by the model, based on the Penman–Monteith equation, was approximately 40% of cumulative IC observed. Underestimation was great in events with long RP, but not with large RFI. We suggest that large amount of IC occurred during rainfall, which is induced by splash droplets transport (SDT) by canopy ventilation.

Rainfall interception and stem flow by eucalypt street trees – The impacts of canopy density and bark type

Understanding how trees influence water movement in an urban landscape is important because in an ‘engineered xeriscape’ small changes in rainfall frequency or magnitude have significant implications to plant water availability and mortality at one extreme, and stormwater runoff and flooding at the other. This study relates direct measures of tree canopy interception and discusses their implication for catchment hydrology in different urban landscape contexts. We measured canopy throughfall and stemflow under two eucalypt tree species in an urban street setting over a continuous five month period. Eucalyptus nicholii has a dense canopy and rough bark, whereas Eucalyptus saligna has a less-dense canopy and smooth bark. E. nicholii, with the greater plant area index, intercepted more of the smaller rainfall events, such that 44% of annual rainfall was intercepted as compared to 29% for the less dense E. saligna canopy (2010). Stemflow was less in amount and frequency for the rough barked E. nicholii as compared to the smooth barked E. saligna. However, annual estimates of stemflow to the ground surface for even the smooth barked E. saligna would only offset approximately 10mm of the 200mm intercepted by its canopy (2010).Tree canopy and bark characteristics should be considered when planting in pervious green space, or impervious streetscapes, because of their profound impact upon tree and surrounding water availability, soil water recharge or runoff. This study provides an evidence base for tree canopy impacts upon urban catchment hydrology, and suggests that rainfall and runoff reductions of up to 20% are quite possible in impervious streetscapes. Street tree canopies can function as a cost-effective compliment to water sensitive urban design for stormwater reduction benefits.

Nitrogen distribution and cycling through water flows in a subtropical bamboo forest under high level of atmospheric deposition.

BackgroundThe hydrological cycle is an important way of transportation and reallocation of reactive nitrogen (N) in forest ecosystems. However, under a high level of atmospheric N deposition, the N distribution and cycling through water flows in forest ecosystems especially in bamboo ecosystems are not well understood.Methodology/Principal FindingsIn order to investigate N fluxes through water flows in a Pleioblastus amarus bamboo forest, event rainfall/snowfall (precipitation, PP), throughfall (TF), stemflow (SF), surface runoff (SR), forest floor leachate (FFL), soil water at the depth of 40 cm (SW1) and 100 cm (SW2) were collected and measured through the whole year of 2009. Nitrogen distribution in different pools in this ecosystem was also measured. Mean N pools in vegetation and soil (0–1 m) were 351.7 and 7752.8 kg ha−1. Open field nitrogen deposition at the study site was 113.8 kg N ha−1 yr−1, which was one of the highest in the world. N-NH4 +, N-NO3 − and dissolved organic N (DON) accounted for 54%, 22% and 24% of total wet N deposition. Net canopy accumulated of N occurred with N-NO3 − and DON but not N-NH4 +. The flux of total dissolved N (TDN) to the forest floor was greater than that in open field precipitation by 17.7 kg N ha−1 yr−1, due to capture of dry and cloudwater deposition net of canopy uptake. There were significant negative exponential relationships between monthly water flow depths and monthly mean TDN concentrations in PP, TF, SR, FFL and SW1.Conclusions/SignificanceThe open field nitrogen deposition through precipitation is very high over the world, which is the main way of reactive N input in this bamboo ecosystem. The water exchange and N consume mainly occurred in the litter floor layer and topsoil layer, where most of fine roots of bamboo distributed.

Graft flow assessment with transthoracic Doppler after coronary arterial bypass grafting with bilateral internal thoracic arteries using Y-graft technique

Purpose — The aim of our study is to assess the transthoracic Doppler parameters of left internal thoracic artery`s stem (LITA) flow after coronary artery bypass surgery with free right internal thoracic artery using Y graft technique and compare them with such parameters of LITA-LAD (left anterior descending) graft flow after regular coronary artery bypass surgery (CABG). Material and Methods — 51 consecutive patients with coronary artery disease underwent CABG. Comparison between groups was performed using the following parameters: age, body mass index, angina class, presence of hypertension and diabetes, left ventricular ejection fraction and hemoglobin level, hemodynamic parameters during the Doppler investigation. Results — Higher systolic acceleration time value in Y graft group is due to bigger runoff of Y graft compared with the classic group. The diastolic acceleration time is shorter in Y graft group as the distal coronary runoff is bigger and LITA`s peak flow accelerate faster. The systolic and diastolic acceleration times are very sensitive parameters which depend on the distal coronary runoff changes. Conclusions — We conclude that blood flow volume in tha LITA graft depend of coronary artery distal run-off and rising when we using to revascularize more than one coronary artery.